Process for producing graft polymer

ABSTRACT

A graft polymer wherein an iodine-containing fluororubber has been grafted on an ethylene-α-olefin copolymer can be obtained by mixing 30 parts by weight of an iodine-containing fluororubber (a vinylidene fluoride-hexafluoropropylene copolymer containing iodine) and 70 parts by weight of an ethylene-propylene copolymer rubber at 180° C. for 30 minutes while applying shear deformation using a Brabender mixer.

The present invention relates to a process for producing a graftpolymer.

Known processes for the production of graft polymer include a processwherein graft polymerization is conducted in the presence of aradical-generating agent such as peroxide or the like. This process,however, has drawbacks that undesirable degradation of polymer takesplace and gelation is caused.

Japanese Patent Application Kokai No. 64-69647 discloses a process whichcomprises dissolving a fluororubber and an ethylene-α-olefin copolymerrubber in a solvent, reemulsifying the resulting solution, andsubjecting the resulting latex to partial crosslinking with an organicoxide. This process, however, requires complicated steps of dissolutionof rubbers, reemulsification, solvent removal and partial crosslinkingof latex and is disadvantageous in the energy required. Thus, theprocess has problems in industrial application.

Japanese Patent Application Kokai No. 1-135851 discloses a process forobtaining a rubber composition by mixing a fluororubber and anethylene-α-olefin copolymer rubber in the presence of a crosslinkingagent (a peroxide) for ethylene-α-olefin copolymer rubber while applyingshear deformation. This process, however, has a drawback that gelationis caused.

It has heretofore been considered that in conducting grafting, the useof a crosslinking agent such as a peroxide or the like is essential.However, when a peroxide or the like is used there is a problem that agel is formed.

Under such circumstances, the present inventors have made extensiveresearch on solving the above problem. As a result, they have foundcontrary to the prior common knowledge that a graft polymer can beobtained efficiently without causing gelation when a specific polymer,i.e. an iodine- and/or bromine-containing polymer is used as anessential constitutive polymer without using a crosslinking agent suchas a peroxide or the like and said polymer and other constitutivepolymer are mixed in the specific temperature range of 130°-300° C.while shear deformation is applied thereto.

According to the present invention, there is provided a process forproducing a graft polymer, which comprises mixing two or moreconstitutive polymers to be grafted, at least one o the constitutivepolymers being an iodine- and/or bromine-containing polymer, in theabsence of any peroxide in the temperature range of 130°-300° C. whileapplying shear deformation.

The present invention is hereinafter described in detail.

In the present invention, the iodine- and/or bromine-containing polymerto be grafted is a polymer containing iodine and/or bromine at theend(s) of its molecular chain and/or in its molecular chain, and thepolymers may be rubbery or resinous.

Said rubbery polymer containing iodine and/or bromine includes, forexample, a fluororubber, an isoprene rubber, a butadiene rubber, astyrene-butadiene copolymer rubber, an acrylonitrile-butadiene copolymerrubber, a butyl rubber, acrylic rubbers (e.g. acrylic rubber,ethylene-acrylate copolymer rubbers, ethylene-vinyl acetate-acrylatecopolymer rubbers), ethylene-α-olefin copolymer rubbers, anethylene-vinyl acetate copolymer rubber, a urethane rubber, apolysulfide rubber, a silicone rubber, etc., all containing iodineand/or bromine. It also includes copolymers obtained by copolymerizingone of said rubbers containing iodine and/or bromine with acrylic acid,methacrylic acid, maleic acid, itaconic acid, allyl glycidyl ether orthe like, and hydrogenation products obtained by partially or whollyhydrogenating the aliphatic conjugated diene portions of one of saidrubbers and natural rubber containing iodine and/or bromine.

The resinous polymer containing iodine and/or bromine includes, forexample, various polyethylenes (e.g. high-density polyethylene or thelike), various copolymers composed mainly of propylene (e.g.polypropylene), an ABS resin, various styrene resins, polyamide resins,polyester resins, fluororesins, etc., all containing iodine and/orbromine.

Of the iodine and bromine in the iodine- and/or bromine-containingpolymer, iodine is preferable in view of the grafting efficiency.

The total content of iodine and bromine in the iodine- and/orbromine-containing polymer is preferably 0.001-10% by weight, morepreferably 0.005-5% by weight. Too low a total content results in aninferior grafting efficiency, and too high a total content tends tocause gelation.

Preferable examples of the iodine- and/or bromine-containing polymer tobe grafted include an iodine-containing fluoropolymer.

The fluoropolymer includes a fluororubber, a fluororesin, afluorine-containing thermoplastic resin, etc.

The iodine-containing fluororubber can be obtained, for example, bycopolymerizing vinylidene fluoride and at least one other fluoroolefinin the presence of a radical-generating source and a compoundrepresented by the general formula R_(f) X_(n) wherein R_(f) is afluorine-containing or fluorine- and chlorine-containing saturated orunsaturated hydrocarbon group, X is iodine, and n is an integer of 1 orlarger, preferably 1 or 2. More particularly, the iodine-containingfluororubber can be obtained by the processes described in JapanesePatent Application Kokai No. 52-40543, No. 53-125491 and No. 63-159336.The above so-called fluororubber includes fluororubbers of vinylidenefluoride/hexafluoropropylene type, vinylidenefluoride/tetrafluoroethylene/hexafluoropropylene type, vinylidenefluoride/chlorotrifluoroethylene type, tetrafluoroethylene/propylenetype, hexafluoropropylene/ethylene type, perfluoroalkyl vinyl ether(including those having a plurality of ether linkages)/olefin (e.g.tetrafluoroethylene, ethylene or the like) type, fluorosilicone type,fluorophosphazene type, etc.

In the present invention, the at least two constitutive polymers to begrafted may be selected from the above-mentioned iodine- and/orbromine-containing polymers, or may be a combination of the aboveiodine- and/or bromine-containing polymer(s) with a polymer other thanthe iodine- and/or bromine-containing polymer(s), for example, ahalogen-free polymer.

The halogen-free polymer may be rubbery or resinous. The halogen-freerubber includes, for example, an isoprene rubber, a butadiene rubber, astyrene-butadiene copolymer rubber, an acrylonitrile-butadiene copolymerrubber, a butyl rubber, acrylic rubbers (e.g. acrylic rubber,ethylene-acrylate copolymer rubbers, ethylene-vinyl acetate-acrylatecopolymer rubbers), ethylene-α-olefin copolymer rubbers, anethylene-vinyl acetate copolymer rubber, a urethane rubber, apolysulfide rubber, a silicone rubber, etc. It also includes copolymersobtained by copolymeriging one of said rubbers with acrylic acid,methacrylic acid, maleic acid, itaconic acid, allyl glycidyl ether orthe like and hydrogenation products obtained by partially or whollyhydrogenating the aliphatic conjugated diene portions of one of saidrubbers. A natural rubber may also be used as the halogen-free rubber.

The halogen-free resin includes, for example, various polyethylenes(e.g. high-density polyethylene or the like), various copolymerscomposed mainly of propylene (e.g. polypropylene or the like), an ABSresin, various styrene resins, polyamide resins, polyester resins,fluororesins and the like.

When there are used, as the constitutive polymers, iodine- and/orbromine-containing polymer(s) and a polymer other than the iodine-and/or bromine-containing polymer(s), the ratio of the amounts of thetwo kinds of polymers used is preferably 70:30 to 5:95, more preferably50:50 to 20:80 in terms of the weight ratio of [the iodine- and/orbromine-containing polymer(s)]:[the polymer other than the iodine-and/or bromine-containing polymer(s)]. When the ratio is larger than theabove range, a part of the iodine- and/or bromine-containing polymer(s)remains without being grafted. When the ratio is smaller than the range,the grafting degree is low.

In the present invention, the temperature at which the constitutivepolymers to be grafted are mixed in the absence of any peroxide whileshear deformation is applied, is 130°-300° C., preferably 130°-250° C.,more preferably 150°-200° C. However, when there is used, as the polymerother than the iodine- and/or bromine-containing polymer(s), a dienetype rubber such as natural rubber, isoprene rubber, styrene-butadienecopolymer rubber, butadiene rubber or the like, the mixing temperatureis preferably 130°-200° C., more preferably 130°-180° C. When a siliconerubber is used, the mixing temperature is preferably 200°-300° C. In anycase, when the mixing temperature is too low, grafting does not proceedsufficiently and, conversely when the mixing temperature is too high,the starting polymers used are thermally degraded.

In the present invention, the mixing while applying shear deformationmay be conducted by using a closed type kneader (e.g. Banbury mixer,Brabender mixer, kneader or the like), an open roll mill, an extruder, acontinuous kneader or the like.

The mixing time is usually 2-60 minutes, preferably 5-50 minutes, morepreferably 5-40 minutes.

In the present process, there can be added to the starting polymers inmixing them conventional compounding agents for rubbers and resins, suchas reinforcing agent, filler, processing aid, plasticizer and the likewhich are all known in the rubber and resin industries.

To the graft polymer obtained by the present process may be added areinforcing agent, a filler, a processing aid, a plasticizer, acrosslinking agent and a crosslinking accelerator when it is practicallyused.

When an iodine- and/or bromine-containing fluororubber is used as theiodine- and/or bromine-containing polymer, the resulting graft polymerretains the excellent properties of fluororubber (e.g. heat resistance,oil resistance, solvent resistance, friction resistance, slipperiness,water repellency, oil repellency and the like) and further is improvedin processability (e.g. dispersion of additives, tackiness and the like)in which conventional fluororubbers are inferior. Owing to theseexcellent features, the graft polymer can be used in wide applications,for example, sealing materials (e.g. oil seal, packing, gasket, O ringand the like), diaphgram, hose lining, coating agent, extruded products(e.g. hose, profile and the like), calendered products (e.g. sheet andthe like) and adhesives.

The present invention is hereinafter described in more detail referringto Examples. However, the Examples are by way of illustration and not byway of restriction.

EXAMPLE 1

Using a Brabender mixer, there were mixed, at 180° C. for 30 minutes, 30parts by weight of an iodine-containing fluororubber [a vinylidenefluoride-hexafluoropropylene copolymer, a product of DAIKIN INDUSTRIES,LTD., Daiel G-902 (trade name), ML₁₊₁₀ 100° C.=55] as an iodine- and/orbromine-containing constitutive polymer and 70 parts by weight of anethylene-propylene copolymer rubber [a product of Sumitomo Chemical Co.Ltd., Esprene 201 (trade name), propylene content=53% by weight, ML₁₊₄100° C.=43] as other constitutive polymer, to obtain a graft polymer.

That the above-obtained poolymer was a graft polymer was confirmed bythe following method.

The iodine-containing fluororubber and ethylene-propylene copolymerrubber used as well as the polymer obtained by mixing them were eachmeasured for the amount extracted with carbon tetrachloride (extractedfor 8 hours at the boiling point of 76.5° C.) (the amount is referred tohereinafter as carbon tetrachloride-extracted amount). The results wereas follows.

    ______________________________________                                                             Carbon                                                                        tetrachloride-                                                                extracted                                                                     amount (wt. %)                                           ______________________________________                                        Iodine-containing fluororubber                                                                       0.1                                                    Ethylene-propylene copolymer rubber                                                                  100.0                                                  Polymer obtained       99.1                                                   ______________________________________                                    

The results are interpreted as follows. The iodine-containingfluororubber having a strong polarity is not extracted with non-polarcarbon tetrachloride. Meanwhile, the ethylene-propylene copolymer rubberis extracted with (dissolved in) non-polar carbon tetrachloride.Therefore, the fact that the major portion (99.1 wt. %) of the obtainedpolymer is extracted with carbon tetrachloride, indicates that theiodine-containing fluororubber used has been grafted on theethylene-propylene copolymer rubber, or degraded into lower molecularsubstances.

Next, the carbon tetrachloride-extracted portion of the polymer obtained(99.1 wt. % of the polymer obtained) was measured for infraredabsorption spectrum. An absorption due to C-F stretching vibration wasseen in the vicinity of 1,200 cm⁻¹. This fact also indicates that theiodine-containing fluororubber used has been either grafted on theethylene-propylene copolymer rubber, or degraded into lower molecularsubstances.

Further, the iodine-containing fluororubber (intrinsic viscosity asmeasured at 35° C. in acetone=0.34 dl/g) alone was kneaded at 180° C.for 30 minutes and then measured for intrinsic viscosity at 35° C. inacetone. The intrinsic viscosity after kneading was 0.33 dl/g which wassubstantially the same as the intrinsic viscosity before kneading. Thisfact indicates that when the iodine-containing fluororubber alone iskneaded a change, e.g. scission of molecular chain or the like is notcaused in the rubber.

By synthesizing the above facts, it is appreciated that theiodine-containing fluororubber was not degraded into lower molecularsubstances but grafted on the ethylene-propylene copolymer rubber.

EXAMPLES 2-5 AND COMPARATIVE EXAMPLES 1-4

The same procedure as in Example 1 was repeated, except that the mixingratio of the iodine-containing fluororubber and the ethylene-propylenecopolymer rubber, the mixing temperature and the mixing time were variedas shown in Table 1. In Comparative Examples 1 and 2, an open roll millwas used in place of the Brabender mixer. The results obtained are shownin Table 1.

In each of Comparative Examples 1-4 in which the mixing temperatureswere lower than the specific range of the present invention, the carbontetrachloride-extracted amount of the polymer obtained corresponded tothe amount of the ethylene-propylene copolymer rubber used (theiodine-containing fluororubber used remained as it was, without beinggrafted). The carbon tetrachloride-extracted portion of the polymerobtained was measured for infrared absorption spectrum, to find that thespectrum was identical with that of the ethylene-propylene copolymerrubber and there was no absorption at 1,200 cm⁻¹ due to C-F stretchingvibration.

COMPARATIVE EXAMPLE 5

The same procedure as in Example 1 was repeated, except that afluororubber free from iodine was used in place of the iodine-containingfluororubber of Example 1 and the mixing ratio was changed as shown inTable 1. The results obtained are shown in Table 1.

The carbon tetrachloride-extracted amount of the obtained polymercorresponded to the amount of the ethylene-propylene copolymer rubberused, and it is appreciated that no graft polymer was obtained.

COMPARATIVE EXAMPLE 6

The same procedure as in Example 1 was repeated, except that theconstitutive polymers were mixed in the presence of an organic peroxideand the mixing ratio was changed as shown in Table 2.

The polymer obtained was subjected to extraction with carbontetrachloride (for 8 hours at the boiling point of 76.5° C.). Theresidue obtained (i.e. the carbon tetrachloride-insoluble portion) wasdried and again subjected to extraction with acetone (for 8 hours at theboiling point of 56.3° C.). The results of extraction are shown in Table2.

The results are interpreted as follows. The iodine-containingfluororubber having a strong polarity is not extracted with (dissolvedin) non-polar carbon tetrachloride. Meanwhile, the ethylene-propylenecopolymer rubber is extracted with (dissolved in) non-polar carbontetrachloride. Further, the iodine-containing fluororubber is extractedwith acetone. Therefore, the acetone-insoluble portion obtained in thistest (about 50 wt. % based on the polymer obtained) is a so-called gelwhich is insoluble in both carbon tetrachloride and acetone, and it isappreciated that the formation of a gel is remarkable when theconstitutive polymers are mixed in the presence of an organic peroxide.Incidentally, the fact that no gel is formed in the present inventionusing no organic peroxide, is also clear from that the carbontetrachloride-extracted amount is substantially 100% (96 wt. % or more)in Examples 1-5.

EXAMPLES 6-15 AND COMPARATIVE EXAMPLES 7-16

The same procedure as in Example 1 was repeated, except that the kindsof polymers, the mixing temperature and the mixing time were changed asshown in Tables 3 and 4. The results obtained are shown in Tables 3 and4. In comparative Examples 7 and 8, an open roll mill was used in placeof the Brabender mixer. Lower mixing temperatures were used inComparative Examples 9 and 12. A fluororubber free from iodine was usedin place of the iodine-containing fluororubber in Comparative Examples10-11 and 13-16.

                                      TABLE 1                                     __________________________________________________________________________                Reference                                                                     Example*.sup.1                                                                          Example             Comparative Example                             1    2    1   2   3   4   5   1   2   3   4   5                   __________________________________________________________________________    Mixing components                                                             Polymer (A)                                                                   Kind        IFKM*.sup.2                                                                        --   IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              FKM*.sup.5          Amount used 100  --   30  50  30  30  50  30  50  30  50  50                  (parts by wt.)                                                                Polymer (B)                                                                   Kind        --   EPM*.sup.3                                                                         EPM EPM EPM EPM EPM EPM EPM EPM EPM EPM                 Amount used --   100  70  50  70  70  50  70  50  70  50  50                  Mixing temperature                                                                        --   --   180 180 150 200 150 40  40  100 100 180                 (°C.)                                                                  Mixing time (minutes)                                                                     --   --   30  30  20  20  20  20  20  10  10  30                  Carbon tetrachloride-                                                         extracted portion                                                             weight %    0.1  100  99.1                                                                              96.0                                                                              99.5                                                                              99.8                                                                              99.5                                                                              76.5                                                                              55.4                                                                              78.8                                                                              56.4                                                                              56.2                IR spectrum *.sup.4                                                                       Seen Not seen                                                                           Seen                                                                              Seen                                                                              Seen                                                                              Seen                                                                              Seen                                                                              Not Not Not Not --                                                            seen                                                                              seen                                                                              seen                                                                              seen                    __________________________________________________________________________     Note:                                                                         *.sup.1 In each Reference Example, each constitutive polymer was used as      it was for measurements without being kneaded.                                *.sup.2 IFKM: a vinylidene fluoridehexafluoropropylene copolymer              containing iodine [Daiel G902 (trade name), ML.sub.1+10 100° C. =      55] manufactured by DAIKIN INDUSTRIES, LTD.                                   *.sup.3 EPM: an ethylenepropylene copolymer rubber (propylene content =       53% by weight, ML.sub.1+4 100° C. = 43) manufactured by Sumitomo       Chemical Co., Ltd.                                                            *.sup.4 IR spectrum: Absorption at 1,200 cm.sup.-1 due to C-F stretching      vibration.                                                                    *.sup.5 FKM: a fluororubber free from iodine [Daial G201 (trade name),        ML.sub.1+10 100° C. = 55) manufactured by DAIKIN INDUSTRIES, LTD. 

                  TABLE 2                                                         ______________________________________                                                               Comparative                                                                   Example 6                                              ______________________________________                                        Mixing components                                                             Polymer (A)                                                                   Kind                     IFKM                                                 Amount used              50                                                   (parts by wt.)                                                                Polymer (B)                                                                   Kind                     EPM                                                  Amount used              50                                                   (parts by wt.)                                                                Organic peroxide*.sup.6                                                       Amount used               3                                                   (parts by wt.)                                                                Mixing temperature (°C.)                                                                        180                                                  Mixing time (minutes)    30                                                   Carbon tetrachloride-extraction residue (wt. %)                                                        80.8                                                 Acetone-extraction residue of carbon                                                                   52.1                                                 tetrachloride-extraction residue                                              (gel content)*.sup.7 (wt. %)                                                  ______________________________________                                         Note:                                                                         *.sup.6 Organic peroxide: 1,3bis(tert-butylperoxyisopropyl)benzene.           *.sup.7 Acetoneextraction residue (gel content): a value obtained when th     weight of the rubber used for extraction with carbon tetrachloride is         taken as 100.                                                            

                                      TABLE 3                                     __________________________________________________________________________                 Reference                                                                           Example                                                                            Comparative                                                                          Reference                                                                           Example                                                                            Comparative                                      Example 3                                                                           6    Example 7                                                                            Example 4                                                                           7    Example 8                           __________________________________________________________________________    Mixing components                                                             Polymer (A)                                                                   Kind         --    IFKM IFKM   --    IFKM IFKM                                Amount used  --    30   30     --    30   30                                  (parts by wt.)                                                                Polymer (B)                                                                   Kind         SBR*.sup.8                                                                          SBR  SBR    CSM*.sup.9                                                                          CSM  CSM                                 Amount used  100   70   70     100   70   70                                  (parts by wt.)                                                                Mixing temperature (°C.)                                                            --    150  40     --    180  40                                  Mixing time (minutes)                                                                      --    30   20     --    30   20                                  Carbon tetrachloride-                                                                      100.0 97.8 73.5   100.0 98.5 69.3                                extracted portion (wt. %)                                                     __________________________________________________________________________     Note:                                                                         *.sup.8 SBR: A styrenebutadiene copolymer rubber [Tufdene 1000R (trade        name), styrene content = 18% by weight, ML.sub.1 +4 100° C. = 45]      manufactured by ASAHI CHEMICAL INDUSTRY CO., LTD.                             *.sup.9 CSM: A chlorosulfonated polyethylene rubber [Hypalon 20 (trade        name), chlorine content = 29% by weight, sulfur content = 1.4% by weight,     ML.sub.1+4 100° C. = 45] manufactured by DuPontShowa Denko Co.,        Ltd.                                                                     

                                      TABLE 4                                     __________________________________________________________________________                 Reference                                                                           Example  Comparative   Reference                                                                           Example Comparative                        Example 5                                                                           8    9   9    10  11   Example 6                                                                           10  11  Example               __________________________________________________________________________                                                            12                    Mixing components                                                             Polymer (A)                                                                   Kind         --    IFKM IFKM                                                                              IFKM FKM FKM  --    IFKM                                                                              IFKM                                                                              IFKM                  Amount used  --    30   50  30   30  50   --    30  50  30                    (parts by wt.)                                                                Polymer (B)                                                                   Kind         EMA*.sup.10                                                                         EMA  EMA EMA  EMA EMA  VMQ*.sup.11                                                                         VMQ VMQ VMQ                   Amount used  100   70   50  70   70  50   100   70  70  70                    Mixing temperature (°C.)                                                            --    180  180 100  180 180  --    220 200 100                   Mixing time (minutes)                                                                      --    30   30  10   30  30   --    30  30  10                    Carbon tetrachloride-                                                                      100.0 92.4 95.1                                                                              73.0 75.6                                                                              48.8 100.0 97.8                                                                              90.5                                                                              72.2                  extracted portion (wt. %)                                                     __________________________________________________________________________     Note:                                                                         *.sup.10 EMA: an ethyleneacrylate copolymer rubber [Esprene EMA2152 (trad     name), acrylate content = 59% weight, ML.sub.1+4 100° C. = 16]         manufactured by Sumitomo Chemical Co., Ltd.                                   *.sup.11 VMQ: a silicone rubber composed of vinylmethylsiloxane,              manufactured by ShinEtsu Chemical co., Ltd.                              

                                      TABLE 5                                     __________________________________________________________________________                 Reference                                                                           Example         Comparative Example                                     Example 7                                                                           12  13  14  15  13  14  15  16                             __________________________________________________________________________    Mixing components                                                             Polymer (A)                                                                   Kind         --    IFKM                                                                              IFKM                                                                              IFKM                                                                              IFKM                                                                              FKM FKM FKM FKM                            Amount used  --    30  30  50  50  30  30  50  50                             (parts by wt.)                                                                Polymer (B)                                                                   Kind         PP*.sup.12                                                                          PP  PP  PP  PP  PP  PP  PP  PP                             Amount used  100   70  70  50  50  70  70  50  50                             (parts by wt.)                                                                Mixing temperature (°C.)                                                            --    200 180 200 180 200 180 200 180                            Mixing time (minutes)                                                                      --    30  30  30  30  30  30  30  30                             Carbon tetrachloride-                                                                      100.0 97.0                                                                              99.0                                                                              93.0                                                                              87.0                                                                              78.0                                                                              78.0                                                                              55.0                                                                              54.0                           __________________________________________________________________________     Note:                                                                         *.sup.12 PP: a polypropylene [Noblen H501 (trade name)] manufactured by       Sumitomo Chemical Co., Ltd.                                              

What is claimed is:
 1. A process for producing a graft polymerconsisting essentially of mixing two constitutive polymers to be graftedin the absence of any peroxide or cross-linkers in the temperature rangeof 130°-300° while applying shear deformation, wherein one constitutivepolymer is an iodine-containing fluoro-rubber containing 0.001-10% byweight of iodine, the other constitutive polymer is an ethylene-α-olefincopolymer rubber, the weight ratio of the iodine-containing fluororubberand the ethylene-α-olefin copolymer rubber is 70:30 to 5:95, the mixingis conducted by using a closed type kneader, and the mixing time is 2-60minutes.
 2. A process according to claim 1, wherein theiodine-containing fluororubber to be grafted is a polymer containingiodine at the end(s) of its molecular chain and/or in its molecularchain.
 3. A process according to claim 1, wherein the mixing isconducted by using a Brabender mixer.